High voltage switch assemblies with sub-atmospheric or vacuum type circuit interrupters for electric power circuits and systems are well known in the art, such as is shown in U.S. Pat. Nos. 4,568,804; 3,955,167 and 3,471,669. Encapsulated vacuum type switches or circuit breakers are also known, as is shown in U.S. Pat. Nos. 3,812,314 and 2,870,298.
Insulated switches using vacuum bottles do not provide means for visual inspection of the contacts to confirm that they are open (visible break) or closed. Prior art switches were designed with contacts in a large gas or oil filled cabinet which allowed a glass window to be installed for viewing the contacts. However, there is no means of directly viewing contacts in vacuum bottles since the bottles are made of metal and ceramic nontransparent materials. The seals required to maintain the vacuum inside the vacuum bottle prohibit the installation of a glass window.
In most switch assemblies and circuit breakers, a pair of contacts acting in cooperation, one fixed and the other movable, are provided for controlling and interrupting current flow. The contacts are housed in a controlled atmosphere contact assembly that includes a glass or ceramic housing, commonly referred to as a “bottle.” A metal bellows is provided on one end of the bottle, and the movable contact is linked to the inside of the bellows. An operating rod attached to the outside of the bellows is moved in order to actuate the movable contact inside the bottle. The interior of the bottle is maintained under a controlled atmosphere, such as air under a low sub-atmospheric pressure, to protect the contacts from damage caused by arcing when the contacts are opened and closed. The glass or ceramic wall of the bottle provides a permeation-resistant enclosure that maintains the controlled atmosphere for the life of the device. Newer high voltage switches combine vacuum switching with high dielectric strength EPDM rubber insulation as described in U.S. Pat. Nos. 5,667,060; 5,808,258; and 5,864,942 to Luzzi, all of which are incorporated herein in their entirety.
Switches that have viewing windows are usually SF6 gas insulated vacuum bottle type switches. In all cases, the contacts within the vacuum bottle are not visible due to the method of construction. A user can view the actuating mechanism through the gas and determine if the mechanism has moved open or closed. This provides a visible indication of the switch position. However, the eventual unavailability of SF6 gas as an insulator due to government regulations and ozone issues is a major disadvantage for the prior art devices. In addition, prior art devices are susceptible to leaks and they have had problems maintaining the SF6 gas within the switch.
The handle positions for prior art switches indicate the position of the contacts in the vacuum bottle. A pointer on the handle indicates closed when pointing in one direction and open when pointing in the other direction. The connection from the handle to the bottle includes a plurality of components which form a linkage. If these components do not function properly, the position of the pointer may not correctly indicate the position of the contacts.
In contrast to the handles on switches, the handle position of an interrupter does not always indicate the contact position even when the actuating mechanism is operating properly. Therefore, interrupters typically have a viewing indicator instead of a pointer. The handle of an interrupter is usually in one direction for closed and the other direction for open. However, the handle can be in the closed position with the contacts open when the interrupter trips due to an over current event. Under these circumstances, the prior art viewing indicator shows that the contact is open but the handle is in the closed position. This is similar to the circuit breakers in a house. When the breaker trips, the handle does not move all the way to the open position and it is necessary to move the handle to the open position in order to reset the mechanism before it can be closed. The linkage from the vacuum bottle to the viewing indicator of the interrupter also includes numerous components (see FIG. 1C), which are subject to failure and a false indication.
Typically, prior art insulated switches using vacuum technology are sealed inside the vacuum bottle and hidden from view. The voltage source and the load are connected to the switch but the switch contacts are not visible. The only means for determining the status of the switch contacts is the position of the switch handle. If the linkage between the handle and the switch contacts is inoperative or defective, there is no positive indication that allows the operating personnel to determine the position of the contacts. This can result in false readings which can be very dangerous to anyone operating the switch or working on the lines. Accordingly, the industry has recognized the need for insulated switches using vacuum bottles that provide a reliable indication of the position of the contacts.